Yiqi Dai

High‐density and high‐speed transceiver modules are essential for coping with the explosive growth of global data traffic. In this work, we demonstrate an ultra‐compact, high‐throughput transceiver module on the lithium‐niobate‐on‐insulator (LNOI) platform. On the transmitter side, the modulator has a footprint of only 100 µm while providing an electrical bandwidth exceeding 110 GHz, enabling 140‐Gbit/s On‐Off Keying (OOK) and 180‐Gbit/s 4‐level Pulse Amplitude (PAM4) operation per channel. Unlike micro‐ring modulators commonly implemented on LNOI, our device features a large 15‐nm free‐spectral range (FSR), theoretically supporting four channels with 3.2‐nm spacing or eight channels with 1.6‐nm spacing. The receiver side employs a multi‐channel flat‐top filter constructed from cascaded Bragg microcavities. The filter offers a 2‐nm 1‐dB bandwidth and insertion loss below 1 dB. Thanks to the tailored microcavity architecture, the total filter length is only about 250 µm. This significant footprint compression on both the transmitter and receiver sides enhances integration density and reduces overall chip area, providing a promising route toward high‐density, high‐speed transceiver modules on the LNOI platform.

Thin-film lithium tantalate (TFLT) is an emerging electro-optic material with properties comparable to lithium niobate and promising applications in communications, sensing, and computing. With advances in wafer fabrication and low-loss dry-etched waveguides, TFLT has gained increasing attention. However, efficient fiber-to-chip coupling remains critical, especially for large-NA fibers that complicate mode conversion. Here, we demonstrate a TFLT large-mode-size edge coupler fabricated by standard semiconductor processes. Coupling to a high-NA fiber (MFD ∼6.5 μm) exhibits losses below 0.5 dB/facet in the O-band, below 0.37 dB/facet in the C-band, and 0.22 dB/facet at 1482 nm. The coupler maintains <1.3 dB/facet across 1200–2400 nm, with high misalignment tolerance and power stability.

Integrated lithium niobate electro-optic modulators are emerging for applications in next-generation optical fiber communication networks. In this work, we demonstrate a polarization-insensitive Michelson interferometer modulator based on a thin-film lithium niobate on insulator platform. By leveraging a mode-conversion-based architecture, the device achieves polarization-insensitive operation while maintaining a low voltage-length product and optical insertion loss. Experimental results show a polarization-dependent loss of 0.36 dB, insertion loss below 0.9 dB, and a half-wave voltage of 11.2 V, corresponding to a voltage-length product of 1.12 V·cm, with an electro-optic bandwidth of ∼21.8 GHz. These performance metrics establish the proposed modulator as a promising candidate for next-generation optical communication systems utilizing standard single-mode fibers, ensuring robust performance in polarization-diverse environments.